System for forming images of heatradiating objects



2 She ets-Sh eet 1 J. EVANS Filed Dec. 28, 1943.

SYSTEM FOR FORMING IMAGES OF HEAT RADIATING OB JECTS July 2, 1946."

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(Ittomeg y J. EVAN 2,403,066

.SYSTEM FOR FORMING IMAGES OF HEAT RADIATING OBJECTS 2 Shegts-Sheet 2 Filed Dec. 28, 1945 ZSmaentor (Ittorueg I Patented July 2, 1946 SYSTEM FOR FORMING IMAGES OF HEAT- RADIATING OBJECTS I John Evans,- Kingston, N. J., assignor to Radio Corporation of America, a corporation of Delaware Application December 28, 1943, Serial No. 515,879

This invention relates to systems for forming images of objects radiating heat and especially to improvements in scanning systems for forming images of heat radiating or heat reflecting bodies. In the prior art devices, such as those disclosed by Wolff U. S. Patent 2,288,766 or Iams U. S.

Patent 2,175,692, a mosaic of heat responsive elements is formed. The resolution of the image of the heat radiating object depends upon the number of elements in the mosaic. If, for example, the mosaic is arranged to form a square of 100 elements high and 100 elements wide, it will take 10,000 elements and the maximum resolution will be limited to a picture of 10,000 elements, which is inadequate for many purposes. On the other hand if the resolution is increased four fold, the mosaic will include 400 by 400 elements or 160,000 elements.- The problem of arranging 10,000 or more separate elements in a mosaic is a real production problem but not the only one; many of the prior art heat responsive elements have been too sluggish or too insensitive. sluggish response lessens the ability of the system'to form a single image which can be seen in its entirety by the human eye; insensitivity limits the useful range.

One of the objects of the present invention is to provide an improved system for forming images of heat radiating or heat reflecting bodies. An-

other object is to provide an improved scanning system for forming images of a heat radiating or heat reflecting object. Another object is to provide an improved system for forming an image of a heat radiating or heat reflecting object in which a line image is formed by a line of heat responsive elements. A further object is to provide an improved system for forming an image of a heat radiating object in which the system is characterized by rapid response and high sensitivity.

The invention will be described by referring to the accompanying drawings in which Fig. 1 is a schematic circuit diagram of a preferred embodiment of the invention; Fig. 2 is a schematic circuit diagram of a modification; and Fig. 3 is an elevational view of the scanning disc employed in the system disclosed by reference to Fig. 1.

Referring to Fig. 1, the heat waves from an object (not shown) are focused by the reflector I and an oscillating mirror 3 through the slit 5 of a scanning disc I. The oscillating mirror, or its equivalent, 'a multisided rotating mirror, may be driven in synchronism with the scanning disc by an eccentric 9 and a link I l or by any suitable driving means. The eccentric may be driven by means of a shaft i3, which is connected at one end to the motor 15 and at the other end of the 6 Claims. (Cl. 178-6-8) gear box IT. The gear ratio determines the ratio of horizontal scanning lines tovertical scanning lines; i. e., for each horizontal line formed by the scanning disc, the mirror 3 is moved to form a second horizontal line, which is displaced vertically whereby the entire field at the heat image is scanned. I

The horizontal line of the heat image is applied through the scanning slot 5 to a linear row of heat responsive units, which are represented by a row of resistors l9. In the present arrangement the heat responsive units are arranged in the plane of the paper to make clear the separate character of'the units, in practice the row of units l9 would be disposed at right angles to the present showing; i. e., normal to the paper. Current from a battery 2| is applied through isolating resistors 23 to each of the heat responsive units. In

the drawings only three of the units are connected to the battery; in practice all of the units i3 would be connected through isolating resistors.

The junctions of each of the resistors 23 and heat responsive units iii are connected through capacitors 25 to the grids of amplifiers 21. The grids may be biased by resistors 29. The output of each of the several amplifiers is applied through a picture amplifier 3| to the control electrode of acathode ray tube 33.

The cathode ray tube is provided with hori zontal and vertical deflecting electrodes 35 and 31 respectively. The horizontal deflecting electrodes 35 are connected to the output of a horizontal deflecting amplifier 39. The input to the amplifier includes a synchronizing generator 4| which consists of a capacitor wheel or armature 43, a fixed plate 45, a battery 41 and connecting resistor 49. A blocking capacitor 5| may be included in the lead to the amplifier 39 to keep the potential of the battery 41 from afiecting adversely the operation of the amplifier.

The vertical deflecting electrodes 31 are connected to the output of a vertical deflecting amplifier 53. The input of the amplifier 53 is connected to a synchronizing generator 55. The generator consists of 'a battery 5'! which is connected through a resistor 59 to a variable capacitor 6|. The variable capacitor consists of a fixed plate and a movable plate. The movable plate oscillates back and forth in synchronism with the'mirror 3. A blocking capacitor 63 may be included in the amplifier input circuit to prevent the potential of the battery 51 from being applied directly to the amplifier. I

The mode of operation of the system of Fig. 1 is essentially as follows: A line" or rectangular 3 portion of heat waves from an object, whose heat image is to be produced. is applied from the reflector l and mirror 3 to the scanning disc 1. Elementary portions of the applied line successively pass through the scanning slot and actuate the particular heat responsive unit l3, which'is then exposed. Each elementary application of the applied heat waves produces a discrete electrical potential change which is applied to the amplifier 21 and hence through the amplifler 3! to the control electrode of the cathode ray tube 33. The amplified electrical potential, applied to the control electrode, varies the intensity of the cathode ray beam.

At the instant the voltage is applied, the oathode ray beam will be impinging on the fluorescent screen of the tube 33 at a position determined by the voltages applied to the horizontal and to the vertical deflecting electrodes 35, 31. The deflecting voltages in turn depend upon the synchronizing generators 4i and 55 respectively. Since the generators are connected to the scanning disc I and to the scanning mirror 3, it follows that as the object, or the heat imagethereof, is scanned vertically and horizontally, the cathode ray beam is moved synchronously across the screen of the tube. Sincefor each elemental area of the heat image there is 9, corresponding beam position and a corresponding beam intensity, it follows that a visible image can be formed on the cathode ray tube fluorescent screen. It is preferable tocomplete the entire scanning cycle in less than one-sixteenth of a second so that the images appear steady. In

some installations a cathode ray tube having a,

persistent fluorescent screen may be used at a slower cyclic rate. The number of horizontal and vertical lines in the scanning pattern depends upon the desired resolution of the image.

While the foregoing system has been described by reference to capacitor synchronizing voltages, it should be understood that the synchronizing voltages may be derived from any suitable source. For example, a potentiometer, driven by the motor l5, maybe substituted for the capacitorgenerator II, or for the generator 3|, as hereinafter described by reference to Fig. In a similar manner any heat detecting units which are sensitive and rapidly responsive may be used. A preferred form of heat responsive unit is described and claimed in applicants copending application Serial No. 515,058, filed Dec. 20, 1943, entitled Heat detection devices and assigned to the same assignee as the instant application.

. The line scanning method lends itself to commutator operation instead of a scanning disc as illustrated in Fig. 2.

Referring to Fig. 2, waves from a heat radiating object II are reflected by a parabolic mir- 'ror 13 and an oscillating mirror I5 onto a row of heat responsive devices 11. The heat responsive device may be of the type disclosed in applicant's application to which reference has been made or the device may consist of any row of heat responsive units which rapidly convert heat waves into discrete electrical waves. The heat responsive units are represented as resistors 19 which are connected to a battery 8| by resistors 83. Each junction of the heat responsive units I9 and resistors 83 is connected through a separate diode rectifier 85 to a separate capacitor 81. The capacitors 81 are separately connected to the fixed contacts 89, a commutator 9i and are connected in common to ground.

The rotatable or movable contact 93 of the I nected to a potentiometer I05 from which horizontal deflecting voltages are derived. The vertical deflecting electrodes II" are connected to a second potentiometer I09 from which vertical deflecting voltages are derived.

The movable contact 33, commutator 3| and the movable portion of the. potentiometer iii! are connected together and are driven synchronously by a motor Ill. The motor III is connected through reduction gears [13 to the second potentiometer I09 and to the oscillating mirror 15. The oscillations of the mirror are established by any suitable reciprocating means such as the eccentric shown in Fig. 1. Here, as in Fig. 1, the heat responsive unit is shown in the plane of the paperi in practice the longitudinal axis of the heat responsive unit should be parallel to the longitudinal axis of the oscillating mirror 15.

The mode of operation of the system of Fig. 2 is not unlike that of the system of Fig. 3. The

' oscillating mirror 15 applies successive horizontal lines of the heat image to be reproduced on the heat responsive detector 11. Each of the elements of the heat detector produces a current change which is proportional to the intensity of the applied heat. These current changes are rectified and the rectified currents are stored in the capacitors 81. The several capacitors are successively discharged as the movable arm 93 engages the fixed contacts of the commutator. The discharge potentials are amplified by the picture amplifier 91 and the amplified potentials are applied to the control electrode 88 thereby to vary the intensity of the cathode ray beam. The beam is moved horizontally and vertically in synchronism with the commutator and oscillating mirror respectively, so that as the.

heat waves are applied to the line of heat responsive units, the cathode ray beam is correspondingly oriented with respect to the fluorescent screen of the tube ilil.

In the system of Fig. 2, the polarity of heat responsive device and the rectifiers may be arranged so that if the background is cold with respect to the object, whose image is to be reproduced, electrical currents will be derived from the object and not from the background, or the polarity may be reversed to image the colder background and not the obiect.

Thus, the invention has been described as an improved method and system for producing visual images of objects radiating or reflecting heat waves. of the heat waves, or may reflect heat waves applied from any source. The heat waves are focused to form a "heat image which is applied in a succession of horizontal lines to a linearly arranged series of heat responsive units. The applied heat waves are converted into electric currents; the currents are amplified; and are applied to a cathode ray tube to vary the beam intensity. The beam is moved horizontally and vertically in synchronism with the application of the heat image to the heat detector.

I claim as my invention:

1. The method ofproducing a visible image of an object radiating heat waves of a length exceeding the longest waves of visible light by That is, the object may be the source ments', and deflecting said cathode ray in syn chronism with the application of said successive lines of said image to said row of elements.

2. The method of Producing a visible image of an object radiating heat waves of a length exceeding the longest waves of visible light by means including a linearly arranged row of heat responsive elements and a cathode ray tube having control and beam deflecting electrodes which includes forming an image of said object corresponding to said radiation, applying successive lines of said image to said row of heat responsive elements to convert said radiations into a series of electrical currents, rectifying each of said currents, storing said rectified currents, successively applying said stored currents to said control electrode in synchronism with the application of said image to said heat responsive elements, and deflecting said cathode ray in synchronism with the application of said successive lines of said image to said row of elements. I

3. The method specified in claim 1 and the additional step of amplifying said electrical currents before application to said control electrode.

4. A system for producing a visible image of an object radiating heat waves of a length greater than the longest waves of visible light including in combination means for forming an image of the heat radiation from said object, a row of heat responsive elements for converting applied heat into electrical currents, means for applying successive lines of said heat image to said elements to convert the applied image into a series of electrical currents, means for rectifying said electrical currents, a cathode ray tube having control and beam deflecting electrodes, means for applying said rectified currents to said control electrode, and means connected to said deflecting electrodes for deflecting said beam synchronously with the application of said lines to said elements.

5. A system for producing a visible image of an object radiating heat waves of a length greater than the longest waves of visible light including in combination means for forming an image of the heat radiation from said object, a row of heat responsive elements for converting applied heat into electrical currents, an oscillating mirror for applying successive lines of said heat image to said elements to convert the applied image into a series of electrical currents, means connected to said elements for rectifying said electrical currents, a cathode ray tube having control and beam deflecting electrodes, a commutator for applying said rectified currents to said control electrode, and means connected to said deflecting electrodes for deflecting said beam synchronously with the application of said lines to said elements.

6. A system for producing a visible image of an object radiating heat waves of a length greater than the longest waves of visible light including in combination means for forming an image of the heat radiation from said object, a row of heat responsive elements for converting applied heat into electrical currents, an oscillating mirrd'r for applying successive lines of said heat image to said elements,.a plura1ity of rectifiers each connected respectively to said elements, capacitors connected to said rectifiers for storing the rectified currents, a commutator connected to said capacitors, a cathode ray tube having control and beam deflecting electrodes, means including said commutator for applying said stored currents to said control electrode in synchronism with the application of said heat image to said elements, and means connected to said deflecting electrodes for deflecting said beam synchronously with the application of said lines to said elements.

JOHN EVANS. 

